Experimental Analysis of Bamboo Strip Perforation Geometry on the Impact Response and Water Absorption of Epoxy Composites

Abstract

Local geometric modification of natural fiber reinforcement offers a non-chemical route for tailoring composite
behavior, but the effect of perforating bamboo strips on mechanical response and moisture uptake remains
insufficiently resolved. This study experimentally evaluated the influence of bamboo-strip perforation
geometry on the impact response and short-term water absorption of epoxy composites. Three-layer cotton
fiber, bamboo strip, and cotton fiber laminates were fabricated by hand lay-up. Charpy impact testing, adapted
from ASTM D6110, compared perforation diameters of 0, 3.2, 4, and 6 mm, while water absorption testing,
adapted from ASTM D570, compared 0, 1, 2, and 3 perforations of 3.2 mm diameter after 1, 2, and 3 h of
immersion five specimens were tested for each variation. Impact strength showed a non-monotonic response,
reaching 200.1 kJ/m² at 6 mm and 157.71 kJ/m² at 4 mm. Water absorption increased with immersion time
in all configurations, while the one and three perforation configurations generally produced lower mean values
than the unperforated control. The results show that perforation geometry should be treated as a configuration
dependent, multi response design variable rather than a uniformly beneficial interfacial modification.
Microstructural characterization and inferential analysis are required to verify the mechanisms underlying
these trends and their statistical robustness.